1. Field of the Invention
The present invention relates to a vehicle ac generator to be mounted in a passenger car or a truck.
2. Description of the Related Art
Recently, weight of the vehicle engine has been reduced as a measure to solve environmental problems, while the derivability of vehicle is improved by increasing engine torque. As a result, the engine vibration is apt to increase although the displacement of the engine is the same. On the other hand, because the vehicle ac generator is mounted on the engine by a bracket to be driven by the engine, the engine vibration is transmitted to the ac generator. Therefore, it is necessary to improve vibration resistant structure of the ac generator. The vehicle ac generator is also required to be more powerful and compact in order to reduce the idling speed of the engine and the space of the engine compartment for securing a sufficient space of the passenger compartment. The reduction in the noise of the vehicle ac generator is also necessary in order to fulfil a social demand to reduce noises that the vehicle makes and a market demand to reduce noises in the passenger compartment. Of course, the above-mentioned improvement should be made at a low cost.
WO98/54823 discloses a compact, powerful and low-noise vehicle ac generator that is comprised of a stator winding that is formed by a plurality of conductor segments. One of the conductor segments that extends from one of plural layers of one of slots is connected to another conductor segment that extends from another layer of another slot. Therefore, a pair of low-resistant three-phase stator windings can be mounted in a stator at a high space factor.
However, there is no suggestion on the vibration resistance of the coil-end of the stator winding, which has a low rigidity despite of a main portion of the vehicle ac generator.
The present invention has been made in view of the above-described problems.
An object of the invention is to provide a vehicle ac generator whose vibration resistant structure is improved by increasing the rigidity of coil-ends of the stator winding.
Another object of the invention is to improve vibration resistant output wires that connect the stator and a rectifier unit.
Another object of the invention is to provide a powerful and inexpensive stator winding by reducing resistance of the stator winding.
Another object of the invention is to provide a low noise stator winding by employing a plurality of windings that are shifted in phase from one another.
In order to attain the above objects according to a feature of the invention, a vehicle ac generator including a field rotor having a plurality of claw-shaped magnetic pole pieces, a stator having a stator core and a multi-phase stator winding and a frame for supporting said rotor and said stator. In such a vehicle ac generator, there are the following features: the stator winding includes at least two pairs of in-slot portions aligned in a depth direction of each of the slots and first and second coil-ends that respectively extend from opposite axial ends of the slots to be disposed thereon; the first coil-end includes a plurality of crossover wires, each of which connects one of the in-slot portions disposed in one layer of first one of the slots and another of the in-slot portions disposed in another layer of second one of the slots that is spaced apart from the first one of the slots by a narrower pitch than a pole-pitch between the N and S poles; and the second coil-end includes a plurality of crossover wires, each of which connects one of the in-slot portions disposed in one layer of third one of the slots and another of the in-slot portions disposed in another layer of fourth one of the slots that is spaced apart from the third one of the slots by the pole-pitch between the N and S poles. Therefore, the height of the first coil-end can be reduced, so that the rigidity of the first coil-end can be increased, thereby increasing the vibration resistance. In addition, the resistance of the first coil-end can be reduced, thereby reducing the heat loss thereof to increase the output power.
According to another feature of the invention, the above-described vehicle ac generator is added the following features: the stator winding comprises a plurality of conductor segments; each of the conductor segments has an inclined portion that crosses an inclined portion of another conductor segment in one of the coil ends and an end portion of the inclined portion; the turn portion is disposed at the first coil end; and a connection portion for connecting the portion of the inclined portion to an end portion of another inclined portion is disposed at the second coil-end. Therefore, the first coil-end becomes hard while the turn portion is formed, so that the rigidity thereof increases further to increase the vibration resistance.
According to another feature of the invention, the above-described vehicle ac generator is added the following feature: one of the in-slot portions disposed in one of the slots is connected in series with another of the in-slot portions that is disposed adjacent the one of the slots, thereby forming a portion of a phase winding of the stator winding. Therefore, it is easy to connect the conductors disposed in the slots that are spaced apart from each other by a shorter pitch than a pole pitch at the first coil-end. This structure can reduce the manufacturing cost thereof.
According to another feature of the invention, the above-described vehicle ac generator is added the following feature: each output line of the stator winding extends from the first coil-end. Therefore, the distance between the first coil-end, whose height can be reduced, and the rectifier unit can be made long enough, so that a radius of a bend corner of an output wire can be large enough to improve the vibration resistance.
According to another feature of the invention, the above-described vehicle ac generator is added the following feature: those of the series-connected conductor segments that are disposed in adjacent two of the slots respectively extend in opposite circumferential directions. Therefore, it is easy to connect the conductors disposed in the slots that are spaced apart from each other by a shorter pitch than the pole pitch, at the first coil-end. As a result, the rigidity of the coil-end can be increased to increase the vibration resistance at a low cost.
According to another feature of the invention, the above-described vehicle ac generator is added the following features: the plural slots are formed of a first slot group that includes slots spaced apart from each other by one pole-pitch and a second slot group that includes slots respectively disposed adjacent the slots of the first slot group and spaced apart from the first slot group by 30 degrees in electric angle; a first multi-phase winding is disposed in the first slot group; a second multi-phase winding is disposed in the second slot group; and output power is separately provided by the first and second multi-phase windings. Therefore, the rigidity of the coil end can be increased to increase the vibration resistance, and the magnetic noise can be reduced by connecting a pair of the multi-phase windings that are 30 degrees in electric angle shifted from each other.